More than we thought
The study refuted previous ideas about the number of stem cells in humans
Svetlana Maslova, Hi-tech+
Stem cells are the main builders in the body. New research by scientists proves for the first time that the number of hematopoietic stem cells in humans is several times greater than previously thought. The discovery challenges all early beliefs about the number of stem cells in other organs.
New research by British scientists proves that the number of hematopoietic stem cells in humans is 10 times greater than previously thought. In the bone marrow of an adult, there are between 50 thousand and 200 thousand of them. The discovery was preceded by the study of stem cells based on the principle of population counting.
All previous estimates of the number of blood stem cells were extrapolated from studies of mice, cats and monkeys. Now, for the first time, scientists have calculated the number of hematopoietic cells in humans. The team isolated several stem cells from human blood and bone marrow and sequenced their genomes to find mutations. Mutations act as barcodes, each of which designates stem cells and their "offspring". Then, by studying the remaining mutations in the blood, the scientists were able to see what proportion of cells carry the same barcodes. As a result, this allowed the researchers to estimate the total number of stem cells in a particular person.
The study assessed the number of stem cells in a 59-year-old healthy man. The work also proves that the number of hematopoietic cells increases significantly in childhood and reaches a peak in adolescence. In adults, the number of cells remains relatively constant, according to the website of the Sanger Institute (UK).
A colony that grew out of a single stem cell of a 59-year-old man. Figure from the Wellcome Sanger Institute Family tree of blood production press release reveals hundreds of thousands of stem cells – VM.
The method has a significant advantage because it analyzes natural mutations in human cells. As a result, it is possible to observe the dynamics of changes in the number of cells during life. "Our approach also allows us to see not only the number of cells, but also how they are interconnected, as well as what types of blood cells are produced. Applying the method to patients with blood cancer, we strive to understand how individual cells displace healthy ones and thus develop cancer," emphasizes the significance of the findings of researcher Henry Lee–Shester.
Article by Henry Lee-Six et al. Population dynamics of normal human blood inferred from somatic mutations is published in the journal Nature – VM.
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